A multicentre gene therapy trial targeting autosomal recessive deafness 9 (DFNB9) reported long-term success, with sustained safety and efficacy outcomes described in Nature in 2026. The treatment is designed to address congenital hearing loss caused by OTOF mutations. The results extend beyond short-term endpoints by providing evidence that therapeutic benefit can persist over longer follow-up horizons in a severe genetic population. For clinicians and developers in inherited hearing loss, DFNB9 is a key test case where durability is often the missing component. Multicentre reporting also matters for translational credibility, since manufacturing variability and procedural differences can influence real-world outcomes. The trial’s sustained performance supports continued expansion and informs regulatory conversations around durability packages. While details on the cohort size and audiometric thresholds were not included in the provided excerpt, the overall headline development is the emergence of durability data strong enough to frame the therapy as a longer-term solution rather than a transient effect.